This invention relates to an intake negative pressure detection apparatus for a multi-cylinder internal combustion engine to detect an intake negative pressure of the multi-cylinder internal combustion engine, and also to a change-over valve suitable for detection of the intake negative pressure.
In an electronic control fuel injection type internal combustion engine (EFI type internal combustion engine), when the amount of fuel injected from an injector provided for each of the cylinders is determined, it is required to know an amount of air flowing in each of the cylinders in an intake step. Since it is difficult to directly know the amount of air flowing in each of the cylinders, there has been performed a method in which a negative pressure sensor for each of the cylinders is provided to detect a negative pressure in the intake passage provided for each of the cylinders (referred to as xe2x80x9cintake negative pressurexe2x80x9d later) and the amount of air flowing in the each of the cylinders is presumed from the detected negative pressure and a volume efficiency of each of the cylinders.
As aforementioned, since the intake negative pressure in each cylinder can be positively detected by providing the negative pressure sensor for each cylinder, the amount of air flowing in each cylinder can be properly presumed. However, as the negative pressure sensor is provided for each cylinder as aforementioned, the expensive negative pressure sensors, the number of which corresponds to the number of the cylinders are required, which causes the cost of the engine to be unavoidably higher.
It will be considered that one negative pressure sensor is commonly provided for two cylinders and connected to the intake pipes of the two cylinders through a fine pipe.
However, since the negative pressure sensor commonly provided and connected to the intake pipes of the two cylinders will measure the average intake negative pressure of the two cylinders, neither variation in air flux between the two cylinders nor the maximum value of the intake negative pressure of each cylinder can be properly measured.
It will be further considered that a negative pressure sensor is connected only to the intake passage of one cylinder among the cylinders so as to detect only the negative pressure in the intake passage of the one cylinder and that the amount of air flowing in the cylinders is presumed in the assumption that the negative pressure in the intake passages of the other cylinders is the same as the detected negative pressure. However, there happens a problem that this method cannot measure variation in the amount of air between the cylinders.
In an internal combustion engine controlled by an electronic control unit (ECU) in various manners, acceleration state and variation in load have been judged from variation in the negative pressure in the intake passages. In the case that only the negative pressure in the intake passage of the selected one of the cylinders is measured, as the acceleration state and the load state vary immediately after the selected cylinder performs the intake step, the variation cannot be detected until the intake step of the next combustion cycle is performed. Thus, the detection of variation in the state of the engine is delayed and this disadvantageously prevents the engine from being properly controlled.
Accordingly, it is an object of the invention to provide an intake negative pressure detection apparatus for a multi-cylinder internal combustion engine adapted to be able to individually detect an intake negative pressure of each of the cylinders using negative pressure sensors, the number of which is fewer than the number of the cylinders.
The invention provides an intake negative pressure detection apparatus for detecting a negative pressure in an intake passage provided for each of the cylinders of a multi-cylinder internal combustion engine, which is adapted to be able to individually detect the negative pressure in the intake passage of the cylinders using one negative pressure sensor.
To this end, in the invention, a common negative pressure sensor is provided for the cylinders of the internal combustion engine and connected through change-over means to intake passages provided for the cylinders, respectively. The change-over means is constructed to introduce into the negative pressure sensor the intake passage pressure having the highest absolute value among the inner negative pressures of the intake passages connected to the change-over means.
In general, the multi-cylinder internal combustion engine never performs the intake step for the cylinders simultaneously and when each cylinder is in the intake step, the absolute value of the negative pressure in the intake passage of the corresponding cylinder is higher than that of the negative pressure in the intake passages of the other cylinders. Thus, with the intake negative pressure detection apparatus constructed as aforementioned, the intake negative pressures of the cylinders can be individually detected. Therefore, according to the invention, the negative pressure in the intake passage of each of the cylinders can be accurately detected without any increase in the cost.
In the invention, a common negative pressure sensor is provided for all the cylinders of the internal combustion engine and connected through change-over means to the intake passages of all the cylinders.
In this case, the change-over means is so constructed as to introduce into the negative pressure sensor the intake passage pressure having the highest absolute value of the inner negative pressure among the pressures of the intake passages connected to the change-over means.
Thus, it will be noted that the change-over means serves to selectively transfer the pressures in the intake passages provided for the cylinders of the multi-cylinder internal combustion engine, respectively, into the negative pressure sensor commonly provided for the cylinders. The change-over means may be formed of a change-over valve constructed as described herein later.
The change-over valve for the change-over means may comprise a valve housing having an intermediate chamber provided inside, first and second pressure detection chambers disposed on both sides of and adjacent to the intermediate chamber, first and second penetration holes provided in a first partition between the first pressure detection chamber and the intermediate chamber and a second partition between the second pressure detection chamber and the intermediate chamber, respectively, a slide member extending through the intermediate chamber and the first and second penetration holes and supported on the first and second partitions in such a manner as it is able to slide along the axial direction thereof, first and second vent holes provided in the first and second partitions so as to communicate the intermediate chamber with the first pressure detection chamber and the intermediate chamber with the second pressure detection chamber, respectively, first and second valve bodies provided on one end of the slide member positioned in the first pressure detection chamber and on the other end of the slide member positioned in the second pressure detection chamber and serving to close the first and second vent holes when the slide member is displaced for predetermined distance on the direction toward the first and second pressure detection chamber, first and second ports provided in the valve housing so as to communicate the first and second pressure detection chambers with outside and a third port provided in the valve so as to communicate the intermediate chamber with outside and the slide member is displaced toward the pressure detection chamber having the lower inner pressure when the first and second pressure detection chambers have the different inner pressures whereby the pressure detection chamber having the lower inner pressure is communicated with the intermediate chamber.
The first and second pressure detection chambers are connected through the first and second ports to pipes through which the pressures in the intake passages of the different cylinders of the internal combustion engine are transmitted while the intermediate chamber is connected through the third port to the negative pressure sensor.
With the change-over valve constructed as aforementioned, the negative pressure detection apparatus for the two cylinder internal combustion engine can be constituted only by the single change-over valve and the single negative pressure sensor while the negative pressure detection apparatus for three or more cylinder internal combustion engine can be constituted by the two or more change-over valves and the single negative pressure sensor to which the intake passages of the three or more cylinders are connected through the change-over valves in tournament form.
More particularly, in case that the negative pressures in the first and second intake passages for the first and second cylinders of the two cylinder internal combustion engine should be detected, the first and second ports of the single change-over valve are connected to the first and second intake passages, respectively and the single negative pressure sensor is connected to the third port of the change-over valve whereby the negative pressures in the intake passages for the two cylinders can be detected. Thus, it will be noted that the change-over means is constituted only by the single change-over valve.
In case that the negative pressures in the first through third intake passages for the first through third cylinders of the three cylinder internal combustion engine should be detected, the first and second ports of the first change-over valve are connected to the first and second intake passages, respectively, the first port of the second change-over valve is connected to the third port of the first change-over valve, the second port of the second change-over valve is connected to the third intake passage of the internal combustion engine and the third port of the second change-over valve is connected to the negative pressure sensor whereby the negative pressures in the intake passages for the three cylinders can be individually detected by the single negative pressure sensor.
Thus, it will be noted that the change-over means for the three cylinder internal combustion engine is constituted by the first change-over valve having the first and second ports connected to the first and second intake passages, respectively, and the second change-over valve having the first port connected to the third port of the first change-over valve, the second port connected to the third intake passage and the third port connected to the negative pressure sensor.
In case that the negative pressures in the first through fourth intake passages for the first through fourth cylinders of the four cylinder internal combustion engine should be detected, the first and second ports of the first change-over valve are connected to the first and second intake passages, respectively, the first and second ports of the second change-over valve are connected to the third and fourth intake passages, the first and second ports of the third change-over valve are connected to the third ports of the first and second change-over valves, respectively and the third port of the third change-over valve is connected to the negative pressure sensor whereby the negative pressures in the intake passages for the four cylinders can be individually detected by the single negative pressure sensor.
Thus, it will be noted that the change-over means for the four cylinder internal combustion engine is constituted by the first change-over valve having the first and second ports connected to the first and second intake passages, respectively, the second change-over valve having the first and second ports connected to the third and fourth intake passages, respectively, and the third change-over valve having the first and second ports connected to the third ports of the first and second change-over valves and the third port connected to the negative pressure sensor.
Otherwise, the intake negative pressures of the multi-cylinder internal combustion engine having a number of cylinders may be detected by more than one negative pressure sensors. For instance, in the four cylinder internal combustion engine, the intake passages of the two cylinders are connected through the change-over means to one of the two negative pressure sensors while the intake passages of the other two cylinders are connected through the change-over means to the other of the two negative pressure sensors whereby the respective negative pressure sensors can detect the intake negative pressures of the two cylinders. In this case, since the number of the negative pressure sensors can be reduced in comparison with the prior art in which the negative pressure sensor is provided for each of the cylinders, the cost for detecting the intake negative pressure can be reduced.
Similarly, the intake negative pressure of the multi-cylinder internal combustion engine which has six cylinders or more may be positively detected by using the negative pressure sensors, the number of which is fewer than the number of the cylinders.
In general, in case that the intake negative pressure of the multi-cylinder internal combustion engine having 2n cylinders (n is an integer of two or more) should be detected, the 2n cylinders are divided into a plural of sets of two cylinders, in which of the same set the intake step is not performed simultaneously, one change-over valve is provided for each set of two cylinders, the first and second ports of the change-over valve for each set of two cylinders are connected to one and the other of the two intake passages for the respective cylinders, respectively and then third port of the change-over valve is connected to the negative pressure sensor provided commonly for each set of two cylinders whereby the negative pressures in the intake passages of the 2n cylinders can be detected by the negative pressure sensors, the number of which is one half of the number of the cylinders.